From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55218) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZZZKr-0003Tu-JC for qemu-devel@nongnu.org; Wed, 09 Sep 2015 02:58:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZZZKo-0006Ca-93 for qemu-devel@nongnu.org; Wed, 09 Sep 2015 02:58:25 -0400 Received: from e28smtp06.in.ibm.com ([122.248.162.6]:60804) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZZZKn-0006CD-KY for qemu-devel@nongnu.org; Wed, 09 Sep 2015 02:58:22 -0400 Received: from /spool/local by e28smtp06.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 9 Sep 2015 12:28:18 +0530 Date: Wed, 9 Sep 2015 12:28:02 +0530 From: Bharata B Rao Message-ID: <20150909065802.GH17433@in.ibm.com> References: <1438838837-28504-1-git-send-email-bharata@linux.vnet.ibm.com> <1438838837-28504-10-git-send-email-bharata@linux.vnet.ibm.com> <20150904070105.GB6537@voom.redhat.com> <55E95A09.8030700@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55E95A09.8030700@redhat.com> Subject: Re: [Qemu-devel] [RFC PATCH v4 09/11] spapr: Support topologies with unfilled cores Reply-To: bharata@linux.vnet.ibm.com List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Thomas Huth Cc: mdroth@linux.vnet.ibm.com, aik@ozlabs.ru, agraf@suse.de, qemu-devel@nongnu.org, qemu-ppc@nongnu.org, tyreld@linux.vnet.ibm.com, imammedo@redhat.com, nfont@linux.vnet.ibm.com, afaerber@suse.de, David Gibson On Fri, Sep 04, 2015 at 10:44:57AM +0200, Thomas Huth wrote: > On 04/09/15 09:01, David Gibson wrote: > > On Thu, Aug 06, 2015 at 10:57:15AM +0530, Bharata B Rao wrote: > >> QEMU currently supports CPU topologies where there can be cores > >> which are not completely filled with all the threads as per the > >> specifed SMT mode. > >> > >> Restore support for such topologies (Eg -smp 15,cores=4,threads=4) > >> The last core will always have the deficit even when -device options are > >> used to cold-plug the cores. > >> > >> Signed-off-by: Bharata B Rao > > > > Is there a reason to support these silly toplogies, or should we just > > error out if this is specified? Only reason was to ensure that existing guest with such topologies continue to boot like before. > > FYI, I've recently submitted a patch that tries to catch such illegal > SMP configurations and simply errors out in that case: > > http://lists.nongnu.org/archive/html/qemu-devel/2015-07/msg04549.html > > It's not upstream yet, but already in Eduardo's x86 branch. I think this > will reject the bad topology from your example, too. It does reject -smp 15,cores=4,threads=4, but with -smp 15,cores=4,threads=4,maxcpus=16, the guest still boots with weird topology. [root@localhost ~]# lscpu Architecture: ppc64 CPU op-mode(s): 32-bit, 64-bit Byte Order: Big Endian CPU(s): 16 On-line CPU(s) list: 0-14 Off-line CPU(s) list: 15 Thread(s) per core: 3 Core(s) per socket: 1 Socket(s): 4 NUMA node(s): 1 Model: IBM pSeries (emulated by qemu) L1d cache: 64K L1i cache: 32K NUMA node0 CPU(s): 0-14 [root@localhost ~]# ppc64_cpu --info Core 0: 0* 1* 2* 3* Core 1: 4* 5* 6* 7* Core 2: 8* 9* 10* 11* Core 3: 12* 13* 14* 15 Should such topologies also be prevented from booting ? Regards, Bharata.